A new family of polar, water-containing aminoplastic embecments has been developed for electron microscopy which permit the retention of lipids in sections, and which also maintain normal spacial relations dependent upon glycocalyx gels. Various staining procedures can be used to differentiate the different layers associated with cytomembranes. It is intended to apply these techniques in studying specific details associated with kidney, lung and intestinal tissue. These studies will include an examination of fenestrated endothelium and the "slit-pores" associated with the glomerular podocytes to assess the distribution and role of surface coats found there. Junctional complexes will be examined in kidney and intestinal epithelial cells to assess the role played by glycocalyx, particularly in relation to "tight junctions". The extracellular compartments created by the deep infoldings of the basal plasma membranes of tubular cells in the kidney will be studied with particular emphasis upon their dimensions. The new procedures will permit visualizing surfactant in the lung, and its formation and distribution will be studied. There is some hope that the new embedding techniques can be combined with improved fixation to yield superior pictures of intracellular filamentous proteins. If so, smooth muscle will become a target of particular interest, for we would like to be able to visualize clearly both thick and thin filaments in the same preparation. In that case, we would use the smooth muscle of the intestinal wall, arterial muscle from the kidney and bronchiolar muscle from the lung.